The present invention is a network of independent and/or interdependent methods to greatly improve data for the DTAC system disclosed in U.S. Pat. No. 8,878,519, which is fully incorporated hereafter. This new data correction system can provide improvements by orders of magnitude in the measured DTAC response accuracy, which allows for greater depth of investigation, improved target location, and enhanced target characteristics.
The DTAC system transmits electromagnetic (“EM”) fields, typically in the range of Hz to kHz, and measures the primary EM field plus the secondary EM fields generated in subsurface targets. The DTAC system uses a reference frequency to define a unique null direction in the EM fields. The DTAC system then measures the EM fields at other frequencies in this null direction. This approach to EM geophysical surveying has many advantages over the current state of the art, including more robust measurements, higher sensitivity and resolution, and reduced sensitivity to surface interference.
EM subsurface detection and imaging systems include a transmitter antenna generating a primary EM field that propagates into the subsurface. A secondary EM field, which is induced as the primary EM field encounters resistivity variations in the subsurface environment, is measured by a receiver. The receiver measures various properties of the received EM field including an in-phase component and a quadrature component to determine the presence, location, depth size and electrical properties of a subsurface target. Application of the present data correction system to EM systems provides improvements in measured response accuracy, which allows for greater depth of investigation, improved target location and enhanced target characteristics.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.